FIG. 7 shows schematically a conventional method of cutting a material by using a laser machine. In FIG. 7, cutting of the material has been accomplished by controlling heat to a portion to be processed by adjusting a position of the focal point of laser beams, an output of the laser beams and a cutting speed depending on the material to be processed. In FIG. 7, reference numeral 1 designates a processing head, numeral 2 designates a focusing lens, numeral 3 designates laser beams, numeral 4 designates a focal point and numeral 5 designates a material to be cut.
When the material is to be cut, the focal point of the laser beams moves on the material along a predetermined path due to relative movement of the processing head with respect to the material to be cut 5, whereby the material is cut in a predetermined shape.
The above-mentioned laser beam processing is a method of cutting by utilizing heat. Accordingly, when insulating material made of paper or the like is to be cut, the phenomena that a cut surface becomes dark due to burning and a material at the cut surface is resinified or is chemically changed may cause deterioration in electrical performance, appearance and so on. The chemically changed material is very sensitive to an input heat at the focal point of the laser beams and locally appears due to a change of cutting speed at a curved portion and a change of focal point position which is caused by deformation of the cut material. This reduces the quality of products to be produced.
Besides the above-mentioned method utilizing heat which causes the problem of a chemical change, there has been proposed a method of cutting a material only by a water jet. However, when a material having a large thickness is to be cut, an extremely large propellent force is needed, which inevitably requires a large-sized apparatus and causes burrs or fuzzing at an edge of a cut portion in the cut material.